It is well-known that collagen is a protein that is very abundant in man. It is found in most tissues and organs and in particular in the skin. Collagen constitutes organized structures and in particular fibers having a length of between one-tenth of a millimeter and several millimeters and a diameter of several hundreds of nanometers, these fibers having transverse striations about every 70 nanometers. These collagen fibers are formed by groups of tropocollagen fibrils, these fibrils forming the basic element constituting human collagenic material.
Several methods have been proposed which extract from animal tissue a collagenic fraction by means of an aqueous solution of an alkaline-metal or alkaline-earth salt (see in particular GOLDSTEIN, C. R. ACADEMIE DES SCIENCES DE PARIS, volume 268, pages 2446-2448 and the bibliography therein), but the collagen thus obtained is not in the form of organized fibers as are found in conjunctive tissue.
It is known in cosmetic surgery to correct skin depressions that are the result of acne, accidental injuries, or simple aging by injecting into these skin depressions a collagenic material. Up to the present the collagenic material that is injected is generally obtained from cattle. The injections are carried out by means of fine needles right at the region of the breaks in the skin. Unfortunately bovine collagen thus in place constitutes relative to the human organism into which it is injected a foreign body which is attacked by an enzyme, collagenase, that is secreted by fibroblasts of the subject under treatment. The result is that the added collagen implaced is reabsorbed in several months so that this type of treatment is not satisfactory. In order to avoid this disadvantage it would be necessary on one hand to be able to place in the skin breaks a collagen of the same type (that is type I and III) of human origin and it would be necessary on the other hand that this collagen be in the form of collagenic fibers in order to be able to reconstitute a skin matrix having the same characteristics as the collagenic matrix of the conjunctive tissue of the subject in the regions adjacent the treated region.